Nozzle arrangement for an inkjet printhead having an ejection actuator and a refill actuator

ABSTRACT

A nozzle arrangement for an inkjet printhead is provided. The nozzle arrangement includes a wafer substrate defining a nozzle chamber and drive circuitry and ink passivation layers defining an inlet to the chamber. An etch stop layer forms a roof layer for the chamber with an ink ejection port defined in the roof layer. The nozzle arrangement also includes an ejection actuator and a refill actuator collectively spanning the inlet, said ejection actuator actuatable via the drive circuitry layer to eject ink from the ejection port, and said refill actuator actuatable via the drive circuitry layer to facilitate refilling of the chamber with ink via the inlet.

REFERENCES TO US APPLICATIONS

The present application is a Continuation application of U.S.application Ser. No. 09/900,160 filed Jul. 9, 2001, now issued U.S. Pat.No. 7,381,340, which itself is a continuation-in-part application ofU.S. application Ser. No. 09/112,778, now issued U.S. Pat. Nos.6,416,168, 6,213,589, 6,247,795, 6,394,581, 6,244,691, 6,257,704,6,416,168, 6,220,694, 6,234,610, 6,247,793, 6,264,306, 6,241,342,6,254,220, 6,302,528, 6,239,821, 6,247,796, 6,557,977 are herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates to ink jet printheads. More particularly, thisinvention relates to an ink jet printhead chip that incorporates an etchstop layer.

BACKGROUND TO THE INVENTION

The Applicant has invented an ink jet printhead that is capable ofgenerating text and images at a resolution of up to 1600 dpi.

In order to achieve this, the Applicant has made extensive use of microelectro-mechanical systems technology. In particular, the Applicant hasdeveloped integrated circuit fabrication techniques suitable for themanufacture of such printheads. The Applicant has filed a large numberof patent applications in this field, many of which have now beenallowed.

The printheads developed by the Applicant can include up to 84000 nozzlearrangements. Each nozzle arrangement has at least one moving componentwhich serves to eject ink from a nozzle chamber. These componentsusually either act directly on the ink or act on a closure which servesto permit or inhibit the ejection of ink from the nozzle chamber. Themoving components are microscopically dimensioned. This is necessary,given the large number of nozzle arrangements per printhead.

Such printheads usually incorporate at least one printhead chip. Wheremore than one printhead chip is required, the printhead chips arealigned to define what can be regarded as a single, elongate chip. Theconstraints on the dimensions of silicon wafers which are availableresult in the necessity for having more than one printhead chip defininga single printhead.

Those of ordinary skill in the field of integrated circuit fabricationtechniques will appreciate that the cost of on-chip real estate isextremely high. It is therefore important that a configuration beselected which is efficient and yet which uses a minimum amount of spacein order to keep costs to a minimum. Furthermore, it should also beborne in mind that integrated circuit fabrication techniques involvewhat is generally a deposition and subsequent etching process. As such,devices manufactured in accordance with such techniques are usuallylayered for ease of construction and also as a result of the methodsused to construct such devices. It follows that it is desirable that thestructure of the printhead together with the method in which theprinthead is manufactured accommodates a layered configuration. Thiswill facilitate ease of construction with a consequent reduction incosts.

The present invention has been conceived by the Applicant in an attemptto provide a printhead chip configuration which effectively overcomesthe difficulties identified above.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodof manufacturing an ink jet printhead, the method comprising the stepsof:

depositing a layer of etch stop material on a front side of a wafersubstrate;

etching the wafer substrate up to the etch stop material to define aplurality of nozzle chambers and so that portions of the etch stop layerdefine roof walls for respective nozzle chambers; and

etching each said portion to form at least one ink ejection port in eachsaid portion.

According to a second aspect of the invention there is provided an inkjet printhead chip that is manufactured in accordance with an integratedcircuit fabrication technique, the printhead chip comprising

a wafer substrate that defines a plurality of nozzle chambers as aresult of an etching process;

an etch stop layer positioned on a front side of the wafer substrate sothat portions of the etch stop layer define a roof wall for each nozzlechamber, each said portion defining at least one ink ejection port, alsoa result of an etching process carried out on each portion; and

a plurality of actuators arranged on a back side of the wafer substrate,each actuator being operatively positioned relative to each respectivenozzle chamber to eject ink from the nozzle chambers.

The invention is now described, by way of example, with reference to theaccompanying drawings. The specific nature of the following descriptionshould not be construed as limiting in any way the broad nature of thissummary.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 shows a three-dimensional, sectioned view of a first embodimentof a printhead chip, in accordance with the invention;

FIG. 2 shows a schematic view of a nozzle arrangement of the printheadchip in a quiescent condition;

FIG. 3 shows a schematic view of the nozzle arrangement of FIG. 2 withan ejection actuator in an operative condition;

FIG. 4 shows a schematic view of the nozzle arrangement of FIG. 2 withthe ejection actuator in a post-operative condition;

FIG. 5 shows a schematic view of the nozzle arrangement of FIG. 2 with arefill actuator in an operative condition;

FIG. 6 shows a schematic view of the nozzle arrangement of FIG. 2 withthe refill actuator in a post-operative condition;

FIG. 7 shows the nozzle arrangement of FIG. 2 again with the ejectionactuator in an operative condition;

FIG. 8 shows an exploded, three-dimensional view of a second embodimentof part of a printhead chip, in accordance with the invention;

FIG. 9 shows a sectioned side view of a nozzle arrangement of theprinthead chip of FIG. 8 in a post-operative condition;

FIG. 10 shows a sectioned side view of a nozzle arrangement of a thirdembodiment of a printhead chip, in accordance with the invention, in anoperative condition; and

FIG. 11 shows a sectioned side view of the nozzle arrangement of FIG. 10in a post-operative condition.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following specific description, reference is made in particularto a nozzle arrangement of a printhead chip, in accordance with theinvention. The reason for this is that the printhead chip comprises aplurality of the nozzle arrangements shown in each of the followingembodiments. Thus, for ease of description and for the sake ofconvenience, reference is made in the following description to a singlenozzle arrangement. It will readily be appreciated that since the nozzlearrangements of the following examples are manufactured in accordancewith an integrated circuit fabrication technique, duplication of thenozzle arrangements on a single printhead chip would be a naturalconsequence of the manufacture of such nozzle arrangements.

In FIGS. 1 to 7, reference numeral 10 generally indicates a nozzlearrangement forming part of a first embodiment of a printhead chip, inaccordance with the invention.

The nozzle arrangement 10 includes a wafer substrate 12. An etch stoplayer 14 is formed on a front surface of the wafer substrate 12. Theetch stop layer 14 is in the form of a layer of boron doped epitaxialsilicon. It will thus be appreciated that the etch stop layer 14provides a suitable etch stop for the etching of the wafer substrate 12to define a nozzle chamber 16. In particular, the etch stop layer 14 cantherefore be provided to define a roof wall 18 of the nozzle arrangement10.

The roof wall 18 is etched to define an ink ejection port 20.

A drive circuitry layer 22 is formed, by a deposition and etchingprocess, on the wafer substrate 12. Specific details of the fabricationof the drive circuitry layer are provided in the above referenced USapplications and will therefore not be described in any detail in thisspecification.

An ink passivation layer 24 is deposited on the drive circuitry layer 22to protect the drive circuitry layer 22. The ink passivation layer 24can be of any suitable material such as silicon nitride.

In this particular example, a layer 26 of expansion material isdeposited on the ink passivation layer 24.

The layer of expansion material 26 is etched to define an ejectionactuator 28 and a refill actuator 30 which span an inlet 32 of thenozzle chamber 16. The expansion material has a coefficient of thermalexpansion which is such that expansion of the material upon heating canbe harnessed to perform work.

Thus, each of the actuators 28, 30 has a heater element 34 positionedtherein. Each heater element 34 is connected to the drive circuitrylayer 22 with suitable vias 36.

Operation of the ejection and refill actuators 28, 30 is clearly shownin FIGS. 2 to 7. Furthermore, the operation and structure of theactuators 28, 30 are set out in further detail in the above referencedapplications. Accordingly, these will not be dealt with in any detail inthis specification.

The significance of the configuration of the nozzle arrangement 10 isthat the nozzle chamber 16 is defined in the wafer substrate 12 with theetch stop layer 14 defining the roof wall 18 which, in turn, is etchedto define the ink ejection port 20. This particular configurationprovides a high accuracy of manufacture. Further, the structure of thenozzle arrangement 10 is monolithic, which in itself provides a low costof manufacture. Still further, the configuration of the layers inhibitsdifferential expansion upon heating thereby enhancing the life of thenozzle arrangement 10.

In FIG. 8, reference numeral 40 generally indicates a nozzle arrangementof a second embodiment of a printhead chip, in accordance with theinvention. With reference to FIGS. 1 to 7, like reference numerals referto like parts, unless otherwise specified.

As with the previous embodiment, details of the structure and operationof the nozzle arrangement 40 are clearly set out in the above referencedapplications.

This particular example utilizes a thermal actuator 42 which includes aheater element 44 that is manufactured of a shape memory alloy. In FIG.8, the heater element 44 is formed into the shape shown while below itstransformation temperature. The heater element 44 is configured so that,above its transformation temperature, the heater element 44 is generallyplanar. The heater element 44 is also configured to be resistivelyheated when a current is passed through the heater element 44. Theheater element 44 is connected to the drive circuitry layer 22 with vias46.

It follows that, when the heater element 44 is resistively heatedthrough a passing of a current through the heater element 44, by way ofthe vias 46, resultant heating of the heater element 44 above thetransformation temperature results in the heater element 44 returning toits planar state. Subsequent movement in the direction of an arrow 48results in the ejection of a drop of ink 50 from the ink ejection port20.

In FIGS. 10 and 11, reference numeral 60 generally indicates a nozzlearrangement of a third embodiment of a printhead chip, in accordancewith the invention. With reference to FIGS. 1 to 9, like referencenumerals refer to like parts, unless otherwise specified.

As with the previous embodiments, details of the manner in which thenozzle arrangement 60 is manufactured and its manner of operation areset out in the above referenced applications.

In this particular example, an actuator in the form of a paddle 62 ispivotally mounted in the inlet 32 of the nozzle chamber 16. The paddle62 has a magnetic core 64. A magnetic field generator is positioned inproximity to the paddle 62 to provide a magnetic field with a repeatedlyreversing polarity. The magnetic core 64 is configured to be sensitiveto this magnetic field. It follows that, unhindered, the paddle 62 tendsto oscillate in time with the repeatedly reversing polarity of themagnetic field.

The sensitivity of the magnetic core 64 and the strength of the magneticfield are such that, on each stroke of the paddle 62, an ink drop 66 iscapable of being ejected from the ink ejection port 20.

In order to achieve selective ejection, a catch mechanism 68 ispositioned in a recess 70 defined in a side wall 72 of the nozzlechamber 16. The catch mechanism 68 is connected to the drive circuitrylayer 22 to be activated by the drive circuitry layer 22 under controlof a suitable control system connected to the drive circuitry layer 22.On activation, as can be seen in FIG. 11, the catch mechanism 68 isdisplaced into the nozzle chamber 16 to engage an edge 74 of the paddle62. Upon such engagement, the paddle 62 is inhibited from moving intothe position shown in FIG. 10. Thus, by activating the catch mechanism68, drop ejection can be inhibited. Thus, selective drop ejection fromthe nozzle arrangement 60 can be achieved.

It will be appreciated that there are many other configurations whichcan be achieved utilizing a nozzle chamber defined in the wafersubstrate with an etch stop layer defining a roof wall of the nozzlechamber. The above examples are simply provided to illustrate a numberof these configurations.

Applicant believes that this invention provides a means whereby aprinthead chip can be manufactured to incorporate the high number ofnozzle arrangements and resultant nozzle arrangement density, as set outin the preamble, at a cost which is competitive and with a minimumamount of complexity. Further, the Applicant believes that thisinvention provides a means whereby the nozzle arrangements can bemanufactured accurately, which is extremely important, given the largenumber of nozzle arrangements per printhead chip. Still further, theinvention facilitates monolithic construction since the nozzle chambersare defined by the wafer substrate and are not positioned on the wafersubstrate as a result of a further process.

1. A nozzle arrangement for an inkjet printhead, said nozzle arrangementcomprising: a wafer substrate defining a nozzle chamber and drivecircuitry and ink passivation layers defining an inlet to the chamber;an etch stop layer forming a roof layer for the chamber, an ink ejectionport defined in the roof layer; and an ejection actuator and a refillactuator collectively spanning the inlet, said ejection actuatoractuatable via the drive circuitry layer to eject ink from the ejectionport, and said refill actuator actuatable via the drive circuitry layerto facilitate refilling of the chamber with ink via the inlet.
 2. Thenozzle arrangement of claim 1, wherein each actuator includes a heaterelement to facilitate actuation through thermal bending of theactuators.
 3. The nozzle arrangement of claim 1, wherein each heaterelement is connected to the drive circuitry layer by means of viasthrough the ink passivation layer.
 4. The nozzle arrangement of claim 1,wherein the roof layer is in the form of a layer of boron dopedepitaxial silicon.
 5. The nozzle arrangement of claim 1, having an inkpassivation layer deposited on the drive circuitry layer, the inkpassivation layer being a layer of silicon nitride.
 6. The nozzlearrangement of claim 5, having a layer of expansion material depositedon the ink passivation layer.
 7. The nozzle arrangement of claim 6,wherein the layer of expansion material is etched to define the ejectionactuator and refill actuator, said expansion material having acoefficient of thermal expansion which is such that expansion of thematerial upon heating can be harnessed to perform work.